Field of Invention
Embodiments described herein relate generally to a semiconductor device and a manufacturing method thereof.
Related Art
A photo engraving process (PEP) is often applied to the process of manufacturing semiconductor. One photo engraving process generally comprises deposition, development, etching, and so on. A gate, a drain, a source, a channel, an etching stop layer, a passivation layer, a pixel electrode, or the like are generally formed by the photo engraving process in a process of manufacturing thin film transistor (TFT) substrate. However, the manufacturing process is complex and the issue of alignment tolerance is also difficult to be solved.
Generally, during the first photo engraving process, an alignment mark is disposed in an non-display region on a substrate at the same time (e.g. the alignment mark is formed while a gate is formed) so the photo mask can precisely form the required stack structure by aligning the alignment mark in the following photo engraving processes. However, after repeated etching steps, the alignment mark is easily etched away due to the excessively thin membrane of stack in the non-display region. Thus, the alignment can't be successfully retained in the following photo engraving processes.
Therefore, what is needed is to provide a semiconductor device and a manufacturing method thereof which can protect the alignment mark from etching for the alignment in the following processes.